There are many tips that are proven to be effective to improve rankings. Here are some Basic guidelines:

BE PRODUCT/SERVICE CENTERED: Make sure you optimize at least one or more of your pages for EVERY product or service you offer.

DON'T SPAM: You should not put in keywords that don't pertain to your site just so you might attract more visitors. Many search engines are looking for various kinds of index spamming and are banning sites entirely that they catch!

WATCH KEYWORD REPETITION: Be careful not to repeat a single keyword more than about six times, since some engines are now penalizing for "excessive" use of keywords. However, you should repeat your primary keywords as many times as feasible since this effects relevancy rankings greatly.